First-pass evaluation of renal perfusion with TurboFLASH MR imaging and superparamagnetic iron oxide particles

First-pass intrarenal hemodynamics were studied with superparamagnetic iron oxide particles and a T2-weighted TurboFLASH (fast low-angle shot) magnetic resonance (MR) imaging sequence. Four groups of five rabbits each were imaged after bolus injection of 40, 100, 140, and 200 mumol/kg iron, respectively. Images were acquired every 1.2 seconds, with an acquisition time of 700 msec. The signal intensity was measured in the cortex, outer medulla, inner medulla, and globally. In preliminary pathologic applications, two rabbits were imaged after ligation of the lumbar ureter and two after embolization of the renal artery. The reproducibility of the normal dynamics was evaluated with a cross-correlation test. On the images, the intravascular progression of the iron particles could be visualized within the cortex and the two compartments of the medulla in all cases. The maximal reduction in signal intensity in the cortex and medulla increased with the dose. The relationship between signal intensity decrease and dose was not linear, and the reproducibility of the signal intensity versus time plots was acceptable only at the 140 and 200 mumol/kg doses. The decrease in signal intensity was reduced and delayed in the embolized and hydronephrotic kidneys.